High frequency oscillator



March-17, 1942. M. A.- ROTE 2,276,879

' HIGH FREQUENCY OSCILLATOR I Fild .Nov. 10, 1939 I LOAD GRID mew/rINVENTOR MELVIN r4. R072 ATTORNEY Z Patented Mar. 17, 1942 2,276,879HIGH FREQUENCY OSCILLATOR.

Melvin A. Rote, Newark, N. J assignor to International TelephoneDevelopment Co. Inc., New York, N. Y., a corporation of DelawareApplication November 10, 1939, Serial No. 303,750

4 Claims. (Cl. 250-36) My invention relates to oscillators of the type.

for generating high frequencies and more particularly to an improvedmethod of constructing a self-controlled oscillator.

An object of my invention is to provide an oscillator having a highdegree of stability.

A further object of my invention is to provide a buffer circuitparticularly adapted to high frequencies. With my invention an amplifierstage to isolate the oscillator from a load is no longer necessary.

- Self-controlled oscillators having a high degree of stability arerelatively diflicult to construct. The instability is increased when theoscillator is connected to a load which varies. The reason for thisincreased instability is the effect of the varying load upon thefeedback circuit from the plate of the oscillator to the grid of theoscillator. By my invention I eliminate the effect of any varying loadin the plate circuit of the self-controlled oscillator upon the feedbackbetween the plate circuit of that oscillator and the grid thereof.

My invention may be more clearly understood by reference to the attacheddrawing wherein:

Fig. l is a diagram of a self-controlled oscillater having in its outputa re-entrant loop circuit;

Fig. 2 is a modification of the circuit shown in Fig, 1.

In Fig. 1 a self-controlled oscillator designated I is connected to twoloops 2 and 3 by means of a link coupling 4. The loops 2 and 3 are of atype shown in the patent to Alford No. 2,147,809, and are particularlyadaptable to a self-controlled oscillator for generating high frequencycurrents. The oscillator may be any oscillator of a well known typehaving. all incidental or stray coupling between the grid and plateneutralized' so as to prevent any internal feedback in the oscillatoritself. The feedback circuit of the oscillator comprises a link 4coupled to the tank or plate circuit 5, the path A and the leads 6 andcoil 6a. coupled to the grid circuit 1. Traveling waves entering theloops 2 and 3 will pass around the loops in opposite directions, and dueto the transposition 8 will produce voltage nodes at the points 9 whichare equi-distant from the connection points of the link coil 4 to theloops. The two halves of the loops are assumed to be identical in allcharacteristics. At the points 9 is connected a balancing circuit H)which has characteristics substantially identical to those of the platecircuit of the oscillator. If a load H and grid coupling leads and coil6 are connected symmetrically on the loops 2 and 3 and between theoscillator plate circuit and balancing, circuit connections, there willbe no effect upon, the voltage nodes at the points 9, provided that boththe load and the grid coupling link have equal impedances. It isapparent, however, that unequal impedances of the load and grid couplinglink circuits may be compensated for by use of I well known couplingmeans, or the loops them-v selves may be used as transformers bychanging the positions of the elements coupled thereto;

Fig. 2 is a modification of the circuit shown in Fig. 1 and is morereadily adapted to explaining the operation of the stabilizing circuit.Referring tothis figure, l2 represents the oscillator plate circuit andt3. the oscillator grid circuit. The

feedback path comprises leads i4, path A, leads 6 and coil 6a. The loops2 and 3 are represented as square in form but bear no relationto the,physical shape of the loops themselves, that is,

the loops may be made of any desired shape and compensating meansinserted to eliminate any disturbances that arise therefrom. Travelingwaves entering the loops 2 and 3 by way of leads [4 will again producevoltage nodes at the points 9. The nodes are maintained at this point aslong as the load I I and the grid coupling circuit 6 present equalimpedances to the loops 2 and 3, and this condition is especiallydesirable since it is preferable to keep all energy possible out of thebalancing circuit ID to prevent waste of energy in that circuit.

Assuming that the circuit is in an oscillating condition, traveling wavewill be sent along the loops 2 and 3, producing nodes at the points 9and supplying energy to the load II and the grid coupling circuit 6. If,for some reason, the load varies in value from its value during thestable condition, there will be an alteration in the transmission ofwaves past the points a and a. In the case that part of the waves istransmitted backward toward the oscillator plate circuit and forwardtoward the balancing circuit, it will be seen that if the distancesalong the arms A, B and C, D are equal the reflected waves will producenodes at the points b and b in a manner similar to the way that nodesare produced at the points 9, when the source of waves is the oscillatorplate circuit. These nodes will be produced at the points b and 12',however, only when the impedances of the oscillator plate circuit andbalancing circuit are identical since unequal impedances would causeunequal attenuations of the reflected'waves passing along the arms A, Band C, D and therefore leave a resultant voltage at the points b and b.

It is readily apparent therefore that any changes in the load II willcreate neutralizing effects at b and b' that cause no alteration in thefeedback energy.

In the preferred form, arm A=arm B=arm C=arm D. However, the importantrequisite is that the path from a, a by way of arms A and B be equal tothe path from a, a to b, b by way of arms C and D. It would be possibleto make arm A equal to arm C and arm B equal to arm D, neither of thesepairs of arms being equal to a each other; or it would be possible tomake arm B equal to arm C and arm A equal to arm D, these pairs of armsalso not being equal to each other. Inequalities in the length of thearms B, C and A, D will cause some of the energy from the oscillatorplate circuit to be fed to the balancing circuit In, and as statedbefore the energy going to the balancing circuit would be an undesirableloss.

In the preferred form, the conjugate networks that I have described havedealt particularly with natural lines designed for use with highfrequencies. It is possible, however, to make the arms of these networksof impedances or artificial lines.

While I have described particular embodiments of my invention forpurposes of illustration, it will be understood that variousmodifications and adaptations thereof may be made within the spirit ofthe invention as set forth in the appended claims:

What is claimed is:

1. An oscillator comprising an output circuit, a conjugate bridgenetwork comprising a reentrant loop circuit connected at one point tosaid output circuit, a balancing circuit connected to said network at asecond point, means for connecting a load circuit to said networkintermediate said points, and an input circuit for said oscillatorconnected to said network and electrically remote from said means.

2. An oscillator comprising an output circuit, a conjugate bridgenetwork comprising a reentrant loop circuit connected at one point tosaid output circuit, a balancing circuit connected to said network at asecond point, means for connecting a load circuit to said networkintermediate said points, and an input circuit for said oscillatorconnected to said network intermediate said points and 180 electricallydifferent in distance from said means.

3. An oscillator comprising an output circuit, a conjugate bridgenetwork comprising a reentrant loop circuit connected at one point tosaid output circuit, a balancing circuit substantially equivalentelectrically to said output circuit connected to said network at asecond point substantially electrically different in distance from saidfirst point, means for connecting a load circuit to said networkintermediate said points and electrically equi-distant therefrom, and aninput circuit for said oscillator connected to said network intermediatesaid points and electrically equi-distant therefrom and 180 electricallydifferent in distance from said means.

4. An oscillator comprising an input circuit and an output circuit, aload circuit, a balancing circuit, a conjugate network comprising atransmission channel having its two ends joined to form a closed loop,connections between said load circuit and a first point of said loop,connections between said input circuit and. a second point of said loopwhose electrical distances along the two halves of said loop to saidfirst point differ by 180, connections from said output circuit and saidbalancing circuit, respectively, to symmetric intermediate points onsaid loop whereby said load circuit is conjugate to said input circuit.

MELVIN A. ROTE.

